NOT APPLICABLE
NOT APPLICABLE
The invention concerns a rotor blade and a wind power installation having a rotor blade, wherein the rotor blade is provided with a rotor blade trailing edge and tapers towards the rotor blade trailing edge.
Rotor blades for wind power installations are known in many different forms. Unfortunately many rotor blades in the state of the art suffer from the problem that in operation of the wind power installation and with wind strengths from about 5 to 6 m/second, they generate not inconsiderable sound emissions, to a not inconsiderable extent. The sound emissions which have occurred hitherto mean inter alia that wind power installations meet resistance on the part of wide classes of society and population, because of the amount of noise generated. As a consequence, wind power installations sometimes encounter difficulty in being accepted or are not accepted at all, as the authorities with responsibility for granting permission for setting up wind power installations refuse such permission because of the environmental considerations involvedxe2x80x94noise also counts as environmental pollution. Therefore, for reasons of noise, particularly in the proximity of residential buildings, it is desirable to reduce the above-mentioned considerable levels of noise emission, in order to satisfy the statutory requirements and to increase the acceptance of wind power installations.
Therefore the object of the present invention is to reduce the level of sound emissions of wind power installations.
In accordance with the invention, with a rotor blade of the kind set forth in the opening part of this specification, that object is achieved in that in the region of the rotor blade trailing edge the degree of taper of the rotor blade increases in a direction towards the rotor blade trailing edge, and there is no stair-like step in the rotor blade at least in that region of the rotor blade.
A particularly advantageous embodiment of the invention is distinguished in that the degree of taper of the rotor blade increases at given spacings in a direction towards the rotor blade trailing edge. In that respect, it is particularly preferable that bends in the cross-section of the trailing edge portion of the rotor blade, that is to say a portion adjacent to the rotor blade trailing edge, are formed at the respective spacings, and between said bends said portion of the rotor blade is substantially flat. Then, in this form of the invention, the planes which are disposed between the bends form very shallow angles relative to each other so that overall the assembly gives approximately the form of a convexly curved surface in respect of the cross-section of the trailing edge portion of the rotor blade.
In a further advantageous embodiment of the rotor blade according to the invention, there are three bends each extending substantially parallel to the rotor blade trailing edge. That embodiment represents an optimum compromise between the expenditure involved in production of the bends in the rotor blade, and a desired marked reduction in the noise level of the rotor blade as it moves.
It is particularly preferred that the inclined planes which adjoin each other in the form of bends and which form the taper configuration for the rotor blade in a direction towards the rotor blade trailing edge are provided only on one side of the rotor blade. In that case it is advantageous if the bends are formed only on the suction or reduced-pressure side of a rotor blade having a pressure side and a reduced-pressure side. That configuration provides for a particularly marked reduction in the level of sound emissions. In that case, it has proven to be desirable that the acute angles which the planes of the reduced-pressure side of the rotor blade, that are between the bends, form with the pressure side of the rotor blade, become increasingly more acute. In that respect, the reduction in the magnitude of the respective angles occurs from the trailing edge towards the leading edge of the rotor blade. The plane portion of the reduced-pressure side of the rotor blade, which is most closely adjacent to the rotor blade trailing edge, then forms the almost sharp rotor blade trailing edge, with the flat pressure side of the rotor blade.
Wind power installations provided with the rotor blade according to the invention overall exhibit a marked reduction in the noise level generated, by virtue of the reduced sound emission of the individual rotor blade. Accordingly, the wind power installations according to the invention represent a markedly reduced noise pollution aspect for the population. Therefore, the wind power installation according to the invention considerably reduces the above-discussed disadvantages of the wind power installations in the state of the art, the level of acceptance of wind power installations on the part of the people is increased and existing anti-noise requirements are more easily met.
Further advantageous embodiments of the invention are set forth in the appendant claims.